Heater Blower Issues

[Dale]

1980 633csi. E12 based car.

Last summer, I totally rehabbed the climate control panel because the resistor inside the panel that controls the fan speed burnt out. I used Peter's great write-up. The AC now blows with variable fan speeds.

I noticed when trying to use the front defogger that there was no air coming out. Investigation showed that the heater fan behind the cowl in the engine compartment was not running.

The fan was replaced with a new Bosch unit 2 summers ago. I also replaced the resistor that is on the fire wall last summer.

When I put the heater and fan on, with my meter hooked up, there is 12.6 volts on the connections. The motor will still not run.

When I turn it off, it is still drawing 3.8 volts.

I bench tested the motor and it spins fine.

I am at a loss why it wont spin while in the car. Connections look good and clean, but I could recheck.

Any thoughts?

Cheers,

Dale
Buffalo, NY
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[Mike W.]

E24s are far more complicated there with the variable speed. You say you have 12V at the motor, is that across the two leads or is it checking either to ground? IIRC, and it's been a while, the E24 blower speed switch goes thru the PC board behind the switch and the transistor up by the blower somewhere, except on high speed, which bypasses everything and provides a straight 12V to the motor. I've only got a somewhat newer wiring diagram, 83 is the oldest I've got, but it appears the ground side goes thru a relay which selects between heater and A/C blowers. If a contact is burned in that relay, or a bad connection somewhere along, the blower would not work. I want to think that relay is on the back of the temp control panel, seems like there's two back there. But it sounds like a ground problem somewhere after the motor. The diagram below is for an 83, which I think is somewhat different, but more similar than an E12.